Dependent Resistivity Measurements Research Articles

In Search of Chiral Molecular Superconductors: κ-[(S,S)-DM-BEDT-TTF]2 ClO4 Revisited.

The relationship between chirality and superconductivity is an intriguing question. The two enantiomeric crystalline radical cation salts κ-[(S,S)-DM-BEDT-TTF]2 ClO4 and κ-[(R,R)-DM-BEDT-TTF]2 ClO4 , showing κ-type arrangement of the organic layers, are investigated in search for superconducting chiral molecular materials following a 1992 report indicating the occurrence of a superconducting transition in the former compound. While the initial interpretation is presently challenged through in-depth temperature and pressure dependent single crystal resistivity measurements combined with band structure calculations, the two chiral conductors show metal like behavior with room temperature conductivities of 10-30 S cm-1 at ambient pressure and stabilization of the metallic state down to the lowest temperatures under moderate pressures. Moreover, their structural and theoretical investigations reveal an original feature, namely the existence of two different κ layers with 1D and 2D electronic dimensionality, respectively, as a consequence of an interlayer charge transfer. The resistivity drop observed for one sample below 1 K and insensitive to magnetic field, possibly results from mixing in-plane and out-of-plane contributions to the measured resistance and suggests current induced charge order melting. This feature contradicts the occurrence of superconductivity in these chiral molecular conductors and leaves open the discovery of the first chiral molecular superconductors.

Grain size dependence of electrical transport in magnetoelectric gallium ferrite ceramics

Engineering microstructural features such as grain size in ceramic materials have strong effect on the various properties of materials. In this manuscript, we demonstrate the effect of grain size on electrical transport in polycrystalline gallium ferrite (GaFeO3 or GFO) samples prepared by solid-state-reaction method. We varied the grain size of the polycrystalline GFO samples by changing the duration of sintering, increasing from 9 μm to 21 μm with the increase in sintering time from 12 h to 256 h at 1350 °C. The samples remain phase-pure without any secondary phase formation upon changing sintering duration. Leakage current density of the samples reduces by nearly four orders of magnitude as the grain size increases from 9 μm to 21 μm. Time and temperature dependent impedance measurements revealed that while the grain boundaries in GFO samples were more insulating than the grains with higher activation energy of 0.65–0.95 eV in comparison to 0.30–0.47 eV for the grains, grain resistivity increases with increase in the sintering duration. Latter is attributed to increasing grain conduction activation energy, caused by migration of oxygen vacancies toward grain boundaries as the sintering time increases resulting in a concomitant decrease in grain boundary conduction activation energy. The study suggests towards a subtle balance between grain and grain boundary conductivities which eventually drive the overall electrical leakage of GFO ceramics. The study also highlights the role of microstructural engineering in tailoring the electrical properties of magnetoelectric GFO ceramics without resorting to atomic substitution.

Pressure dependence of antiferromagnetic and superconducting phases in U2Rh1−xPtxC2

We report temperature ($T$)- and pressure ($P$)-dependent resistivity measurements on the isostructural compounds ${\mathrm{U}}_{2}\mathrm{R}{\mathrm{h}}_{1\ensuremath{-}x}\mathrm{P}{\mathrm{t}}_{x}{\mathrm{C}}_{2}$ ($x=0$, 0.5, and 0.9) from which we construct a $T\ensuremath{-}P\ensuremath{-}x$ phase diagram. Compounds with $x=0$ and $x=0.5$ are antiferromagnets below 22.1 and 9.4 K, respectively, and their N\'eel temperature $({T}_{N})$ decreases under applied pressure. For $x=0$, the critical pressure ${P}_{c}$ required to suppress ${T}_{N}$ to zero temperature is projected to be about 8.8 GPa, but ${P}_{c}$ for $x=0.5$ is between 1.6 and 2.1 GPa. At atmospheric pressure, increasing Pt concentration in ${\mathrm{U}}_{2}\mathrm{R}{\mathrm{h}}_{(1\ensuremath{-}x)}\mathrm{P}{\mathrm{t}}_{x}{\mathrm{C}}_{2}$ tunes magnetic transition temperatures to zero at a critical value of ${x}_{c}\ensuremath{\approx}0.7$, and, consequently, we surmise the existence of a quantum-phase boundary in the $P\ensuremath{-}x$ plane at $T=0$ K that extends from ($P=0, x={x}_{c}$) to (${P}_{c}\ensuremath{\approx}8.8\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}, x=0$). For $x=0.9$, superconductivity appears at ${T}_{\mathrm{c}}=1.09\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, which decreases at a rate of $\ensuremath{\approx}\ensuremath{-}1\phantom{\rule{0.16em}{0ex}}\mathrm{K}/\mathrm{GPa}$ that is nearly twice that found for ${\mathrm{U}}_{2}\mathrm{Pt}{\mathrm{C}}_{2}$ whose ${T}_{\mathrm{c}}$ is 1.47 K. Together, these results indicate that domes of magnetism and superconductivity formed with $T\ensuremath{-}P\ensuremath{-}x$ variations are detached and that the two broken symmetries are independent of each other. Fluctuations in average composition produce rare regions that play an important role in determining physical properties of materials with noninteger $x$.

Growth of large scale PtTe, PtTe2 and PtSe2 films on a wide range of substrates

1T phase of transition metal dichalcogenides (TMDCs) formed by group 10 transition metals (e.g. Pt, Pd) have attracted increasing interests due to their novel properties and potential device applications. Synthesis of large scale thin films with controlled phase is critical especially considering that these materials have relatively strong interlayer interaction and are difficult to exfoliate. Here we report the growth of centimeter-scale PtTe, 1T-PtTe2 and 1T-PtSe2 films via direct deposition of Pt metals followed by tellurization or selenization. We find that by controlling the Te flux, a hitherto-unexplored PtTe phase can also be obtained, which can be further tuned into PtTe2 by high temperature annealing under Te flux. These films with different thickness can be grown on a wide range of substrates, including NaCl which can be further dissolved to obtain free-standing PtTe2 or PtSe2 films. Moreover, a systematic thickness dependent resistivity and Hall conductivity measurements show that distinguished from the semiconducting PtSe2 with hole carriers, PtTe2 and PtTe films are metallic. Our work opens new opportunities for investigating the physical properties and potential applications of group 10 TMDC films and the new monochalcogenide PtTe film.

High quality epitaxial Mn2Au (001) thin films grown by molecular beam epitaxy

The recently discovered phenomenon of Néel spin–orbit torque in antiferromagnetic Mn2Au [Bodnar et al., Nat. Commun. 9, 348 (2018); Meinert et al., Phys. Rev. Appl. 9, 064040 (2018); Bodnar et al., Phys. Rev. B 99, 140409(R) (2019)] has generated huge interest in this material for spintronics applications. In this paper, we report the preparation and characterization of high quality Mn2Au thin films by molecular beam epitaxy and compare them with magnetron sputtered samples. The films were characterized for their structural and morphological properties using reflective high-energy electron diffraction, x-ray diffraction, x-ray reflectometry, atomic force microscopy, and temperature dependent resistance measurements. The thin film composition was determined using both inductively coupled plasma optical emission spectroscopy and Rutherford backscattering spectrometry techniques. The MBE-grown films were found to show a superior smooth morphology and a low defect concentration, resulting in reduced scattering of the charge carriers.

Laser-scribed graphene (LSG) as new electrode material for impedance-based cellular assays

Impedance-based monitoring of cell-based assays has evolved to a multi-functional tool in fundamental and applied biomedical research. The majority of studies rely on gold-films as the electrode material which serves as growth surface and electrode at a time. Besides all its favorable properties like inertness, biocompatibility and superior electrochemical characteristics, gold-film electrodes in contact to cell culture medium show a capacitance of the electrode/electrolyte interface that may become limiting for the sensitivity of the readout. This study describes the use of laser-scribed graphene (LSG) as an alternative electrode material in impedance-based cell monitoring. LSG electrodes are prepared from commercial polyimide foils by simple CO2-laser-induced carbonization. The resulting electrodes show a 25times larger interface capacitance than standard gold-film electrodes due to their foam-like surface topography. Furthermore, LSG-electrodes are (i) highly compatible with cell attachment, (ii) easy to prepare in customized geometries from μm to cm with tunable surface topography and (iii) accessible by roll-to-roll production lines. We conclude from time- and frequency dependent impedance measurements of cell-covered LSG electrodes in direct comparison to the reference material gold that LSG provides an enormous potential to improve the sensitivity of impedance-based monitoring and electric-field mediated manipulation of adherent cells.

An in situ electrical transport measurement system under ultra-high vacuum.

Low-dimensional materials exhibit exotic properties and have attracted widespread attention. However, many low-dimensional materials are highly sensitive to air, making it challenging to investigate their intrinsic properties with ex situ measurements. To overcome such challenges, here, we developed a system combined with sample growth, electrode deposition, and in situ electrical transport measurement under ultra-high vacuum condition. The in situ deposition of electrodes enables desired ohmic electrical contacts between the probes and samples, which allows continuous temperature dependent resistance (R-T) measurements. Combined with a scanning tunneling microscope, surface morphology, electronic structure, and electrical transport properties of the same sample can be systematically investigated. We demonstrate the performance of this in situ electrical transport measurement system with three-unit-cell thick FeSe films grown on Nb-doped SrTiO3(001) substrates, where a low-noise R-T curve with a zero-resistance superconducting transition temperature of ∼30 K is observed.

A strategy for in situ determination of self-healing state for strain hardening cementitious composites

In strain-hardening cementitious composites, the bridging effect of fibers can control crack openings to very small values so the cracks can be self-healed in the presence of water. To rely on autogeneous self-healing to enhance the durability of structures, a method to assess the state of self-healing is required. A new strategy is presented in this paper for in-situ measurement of the healing effect without pre-knowledge of the environmental condition (such as moisture). Exploiting the fact that the electrical conductivity in the crack is lower than that of the undamaged section, the effective macroscopic cracking effect is first distinguished by frequency dependent impedance measurements both along (parallel to) and across the cracks. Dielectric spectroscopy along the cracks is found to correlate well with gravimetric measurements and can therefore, be used for inverse approximation of moisture content. The effect of moisture change on the equivalent resistance in the direction across the cracks can then be derived approximately from measurements under various moisture contents. The approximated resistance vs moisture curve is found to reflect the evolution of autogenous self-healing, and a curve indicating almost complete healing agrees well with the recovery in member stiffness measured from loading test.

Probing TES Transitions by Lead-Position- Dependent Resistance Measurement

We explore the possibility of studying the transition physics of transition edge sensor (TES) devices by performing resistance measurement on voltage leads that are fabricated at different locations along the sample edge. Our Scheme is based on the premise that how the measured resistance depends on the positions of the voltage and current leads are dictated by the underlying physics of the device. To verify its validity and effectiveness, we measure the position dependence of the resistance at temperatures above the critical temperature of the TES, where it is known to obey Ohm's law, and find that the results are in excellent agreement with theoretical predictions. We then perform preliminary measurement in the transition region, by using a superconducting quantum interference device (SQUID) sensor and a lock-in amplifier in a voltage biased circuit subject to a small ac stimulus. Although no theoretical models are available for comparison, the results show significant discrepancy from normal state values and indicate nonuniformity in the TES sample in the transition region. Our technique can be used in further studies to probe TES devices with more conventional lead designs and help understand their transition physics, which can lead to improved device design and operation.

Impact of rare earth substitution on structural and optical properties of multiferroic La2−xGdxNiMnO6

Polycrystalline La2−XGdXNiMnO6 (x = 0.0, 0.5 and 1.0) double perovskites were synthesized by auto combustion sol-gel method. The prepared samples have monoclinic phase with space group P21/n, revealed by Rietveld analysis of x-ray diffraction (XRD) pattern. The analysis of reflectivity spectrum showed well resolved infrared (IR) active phonon modes. We discuss the results in terms of different phonon bands originated as a result of atomic vibrations. Optical energy band gap (Eg) has been estimated from optical conductivity (σ1 (ω)) spectrum and UV-visible absorption spectrum. Temperature dependent resistivity measurements suggest variable range hopping conduction mechanism in these multiferroics.

Partial carrier freeze-out at the LaAlO3/SrTiO3 oxide interface

High quality robust two-dimensional electron gas (2DEG) LaAlO3/SrTiO3 (LAO/STO) interfaces are produced using pulsed laser deposition and an acid-free substrate Ti-termination process, resulting in single unit cell terraces. Temperature dependent resistance measurements show two hysteresis anomalies around 80 K and 160 K. By using Hall measurements, we find an Arrhenius dependence in charge carrier density describing a partial carrier freeze-out below ∼80 K. We show that these two resistance anomalies are unrelated to the temperature dependence of the charge carrier density despite the tempting coincidence of the low temperature hysteresis feature and the freeze-out process. A two-carrier model is required to accurately estimate the activation energy of the thermally activated type charge carriers, which are found to be ∼5 to 7 meV. These results support the theory that oxygen vacancy defects contribute to the metallic conductivity at the 2DEG LAO/STO interface even for annealed samples.

Study of the influence of mechanical pressure on the performance and aging of Lithium-ion battery cells

The influence of an applied mechanical pressure on the electrochemical performance and the aging of 1.4 Ah graphite/NMC622 stacked Lithium-ion battery cells (LiBs) is investigated comprehensively on the electrode and the full cell level. Pressure dependent ionic pore resistance measurements reveal an increase of the ionic pore resistance in both, the anode and the cathode of 6% and 2.9%, respectively at a pressure of 0.84 MPa. Compressibility measurements expose an interesting nonlinearity of the compressibility and the number of layers in an electrode stack, which must be considered for the cell application. The applied pressure improves the electrical contact in the cell. However, by the increase of both, the ionic pore resistance and the charge transfer resistance, the reversible capacity loss is strongly dependent on the applied C-rate during the cycling. For C-rates above 0.8C the polarization losses of the compressed cells are around 7.3% in comparison to 2.1% for the uncompressed cells. Contrariwise, for C-rates below 0.8C the compression of the cells is beneficial and leads to a capacity increase of 2.0% compared to the uncompressed cells. The subsequent post-mortem analysis demonstrates the negative influence of the absence of a homogeneous pressure distribution within the uncompressed cells.

Influence of nanoscale TiO2 film thickness on gas sensing properties of capacitor-like Pt/TiO2/Pt sensing structure

Due to the combustible and explosive nature of hydrogen, it is important to keep its safety during the production, storage, transportation and utilization. To this context, new type of sensors based on TiO2 nano-films with 100, 50 and 30 nm thickness and capacitor-like sandwiched Pt/TiO2/Pt structure were fabricated to monitor the hydrogen leakage. The gas sensing tests indicate that sensing performance improved with the decrease of TiO2 film thickness thus the sensors with 30 nm thick TiO2 film show higher performance in terms of response (6.16 × 104 to 1000 ppm H2) and response time (25.2 s). Moreover, tests also prove that humidity shows a negative effect on the performance. To investigate the sensing mechanism, temperature dependent resistance (R-T) and voltage dependent current (I-V) measurements was performed. The structure and surface topography of the TiO2 film is characterized by the GIXRD and AFM, respectively. In addition, the elemental depth profile of the sensor was studied by the XPS, about 0.9 at.% Pt element was clearly observed in the middle region of the annealed TiO2 layer. Based on the hydrogen diffusion, sensing mechanism of the presented structures is discussed.

Highly oriented (111) CoO and Co3O4 thin films grown by ion beam sputtering

We demonstrate that ion beam sputtering is a suitable deposition technique to obtain single-phase and highly (111)-oriented CoO and Co3O4 thin films. The control of substrate temperature and composition of the reactive atmosphere during deposition allows tailoring the phase structure and preferential growth of the films. Optimum substrate temperatures of 773 K and 603 K for CoO and Co3O4, respectively, have been determined and the presence of the single CoO and Co3O4 phases on the films has been confirmed by X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies. Transmittance differences in the visible region higher than 50% have been observed between low transmittance in Co3O4 films and high transmittance in CoO films. The semiconducting behavior of Co3O4 thin films was confirmed by temperature dependent resistance measurements. The Co3O4 thin films also show a dual optical band gap at energies of 1.47 and 2.14 eV associated to d-d and p-d transition, respectively. Additionally, at intermediate temperatures between the optimum ones to growth (111)-oriented single phase CoO and Co3O4 films, only one single phase, either CoO or Co3O4, is present in the films, in which the electrical and structural properties can be controlled by the oxygen partial pressure used during deposition.

Substrate mediated nitridation of niobium into superconducting Nb2N thin films for phase slip study

Here we report a novel nitridation technique for transforming niobium into hexagonal Nb2N which appears to be superconducting below 1K. The nitridation is achieved by high temperature annealing of Nb films grown on Si3N4/Si (100) substrate under high vacuum. The structural characterization directs the formation of a majority Nb2N phase while the morphology shows granular nature of the films. The temperature dependent resistance measurements reveal a wide metal-to-superconductor transition featuring two distinct transition regions. The region close to the normal state varies strongly with the film thickness, whereas, the second region in the vicinity of the superconducting state remains almost unaltered but exhibiting resistive tailing. The current-voltage characteristics also display wide transition embedded with intermediate resistive states originated by phase slip lines. The transition width in current and the number of resistive steps depend on film thickness and they both increase with decrease in thickness. The broadening in transition width is explained by progressive establishment of superconductivity through proximity coupled superconducting nano-grains while finite size effects and quantum fluctuation may lead to the resistive tailing. Finally, by comparing with Nb control samples, we emphasize that Nb2N offers unconventional superconductivity with promises in the field of phase slip based device applications.

Effect of Co Doping on the Superconducting Properties of Polycrystalline Fe1.01-xCoxTe0.52Se0.48

In the present work, we have studied the effect of Co doping on the superconducting and structural properties of iron chalcogenides Fe1.01-xCoxTe0.52Se0.48 (x = 0, 0.03, 0.05, 0.06) polycrystalline samples. X-ray photoelectron spectroscopy (XPS) has been done at the surface of the samples to study the electronic structure of the material. The temperature dependent resistivity measurements show that the superconducting transition temperature (TC) decreases with the increasing doping concentration of Co. From the magnetoresistance measurements, the superconducting parameters like upper critical field HC2(0) and corresponding coherence lengths (ξ0) have been calculated and it has been observed that values of HC2(0) decrease with the increasing content of Co. Using the Ginzburg-Landau (GL) theory, the estimated values of HC2(0) are 231.8 T and 122.9 T for x = 0 and 0.06 respectively, which are higher compared with the previously reported values of HC2(0) for polycrystalline iron chalcogenide superconductors. From the broadening of superconducting transitions, the values of activation energy (U0) of the thermally activated vortices at different magnetic fields are calculated using the conventional Arrhenius law. It has been observed that U0(H) shows a weak field dependence in low fields ( 2 T) it shows strong field dependence, suggesting the crossover from the single to collective vortex pinning as magnetic field exceed 2 T.

Martensitic ferromagnetism and spin glass behaviour in Ni47Mn36Cr4Sn13 ribbons

Ni47Mn36Cr4Sn13 ribbons were prepared by melt-spinning of the as synthesised bulk alloy. The room temperature structure of the ribbon is dominantly cubic L21 with small admixture of the martensitic orthorhombic phase. The dominance of odd superlattice peak (111) over (200) peak suggests noticeable presence of chemical disorder and hence antisite defects. The temperature dependent resistivity and magnetization measurements unravel the martensitic phase (MP) around ∼360 K in the high temperature austenite phase (AP), while the AP-MP transition occurs at 307 K during cooling and the reverse appears at 328 K in warming cycle. The low field magnetoresistance is rather small and exhibits nonlinear temperature dependence in the low field region. A robust re-entrant ferromagnetic transition whose magnetic moment is almost thrice that of the austenite phase occurs in the martensitic phase. At further lower temperatures, the ferromagnetic transition is succeeded by a re-entrant spin glass (RSG). The analysis of the frequency dispersion of the spin freezing temperature within the Vogel-Fulcher law yields a high value of activation energy (Ea ≈ 50.8 meV) and smaller time constant (τ = 3.28 × 10−12 s) as compared to usual SG behaviour generally observed in Heusler ribbons. However, alternative analysis in terms of the dynamic scaling law validates the canonical nature of the spin glass and hence appears to be better option for analysing the spin glass states associated with the re-entrant ferromagnetism.

Polar axis oriented crystal growth induced carrier transport characteristics in non-degenerate zinc oxide thin films grown on glass substrates

Abstract The predominance of the methanol, ethanol, and 2-methoxyethanol solvents, with different boiling points and dielectric constants, are observed on the crystal growth orientation, optical behavior, carrier recombination, and carrier transport mechanism in sol-gel spin coated ZnO thin films. Multi-axis oriented crystal growth orientation was observed for methanol processed ZnO film as compared to that along c-axis only while using other solvents. The intensity of c-axis orientation, crystallite size as well as radiative recombination luminescence effects follows a direct (or inverse) relationship with the boiling point (or dielectric constant) of the involved solvent. Diverse nature of stress was seen for the films. Ideal band gap value (3.36 eV) was identified for 2-methoxyethanol processed oxygen defects induced stress free ZnO thin films. Time resolved photoluminescence (TRPL) spectra reveal a significant contribution of ultrafast and fast decay components in ethanol and methanol processed films as compared to the dominance of slow decay components in 2-methoxyethanol processed thin film. The temperature dependent electrical resistivity measurements unfold the coexistence of metallic and semiconducting behavior in all films. Dominant optical phonon scattering and piezoelectric scattering mechanisms provide metallic behavior to the films as confirmed by an increasing resistivity with increased temperature. The dominant grain boundary scattering mechanism controls the mobility of the carriers and results in the semiconducting behavior in all films at different values of higher temperatures. We have quantified the crystallite size induced band bending effect to understand the applicability of ZnO films in optoelectronic devices as well.

Magneto-electric field induced activation energy in LSMO imbedded YBCO superconductor

Thick films of YBa2Cu3O7-δ/La 0.67Sr0.33MnO3 have been prepared by diffusion reaction technique. The phase formation and surface morphology have been analyzed through XRD and SEM. From temperature dependent resistivity measurement, under the application of magnetic field, the broadening of resistive transition in the grain boundary region attributes to dissipative of flux pinning. The transition temperature (Tc) and onset of global superconductivity (TC0) marked decreasing value and the resistive broadening is more prominent below the critical temperature in presence of magnetic field for La 0.67Sr0.33MnO3 incorporated into YBa2Cu3O7-δ. From the slope of the Arrhenius plot, we have calculated the activation energy for thermally activated flux flow. Using the Ambegaokar and Halperin phase-slip model, both the magnetic and electric field dependence of activation energy has been interpreted. The above phase slip model followed a power law as (1-t)q with q = 1/2 and t = (T/Tc) has been discussed. The field independent metallic region above 100 K that follows a weak localization effect is being verified.

Degradation in fundamental characteristic features of Bi-2212 superconducting ceramic material with Sr/Ti partial substitution

The present work investigates the vital differentiations in some basic characteristic properties including the crystallinity quality, flux pinning mechanism, superconducting, dc electrical features, grain boundary coupling problems and strength of connection between the superconducting grains in the poly-crystallized Bi2.1Sr2.0−xTixCa1.1Cu2.0Oy cuprate ceramic materials with the partial aliovalent substitution of Sr2+ impurities for the Ti4+ foreign additives in the crystal system. All the materials are prepared by the standard solid-state reaction method, and the characterization of samples produced is thoroughly performed by the typical experimental measurements such as dc electrical resistivity over the temperature, critical current density and powder X-ray diffraction investigations. It is obvious that all characteristic properties tend to diminish constantly with the augmentation of the aliovalent Sr/Ti partial replacement level, and in case of x = 0.10 they reach the global minimum values. To illustrate, the low Bi-2212 superconducting phase diverges from the stabilization because of new induced permanent crystal structure (crystallinity) problems such as the voids, porosity, defects, texturing, cracks, grain boundary coupling problems, grain alignment distributions, stress raisers, omnipresent flaws and crack initiation sites in the crystal system. Besides, the presence of Ti impurities leads to the formation of new impurity phases related to very low superconducting and characteristic TiO2 phase, being favored by either the decrement of c lattice cell parameter or increment of a-axis length. The similar findings are observed in the temperature dependent electrical resistivity measurements. Namely, the electrical resistivities at the normal state are found to increase dramatically from about 74.75–180.47 mΩcm whereas the offset and onset critical temperature values are recorded to diminish from 82.11 K (for the pure sample) to 50.52 K (for the sample prepared with x = 0.10 substitution level) and 84.03–75.14 K, respectively, with the enhancement in the substitution level. Likewise, the Sr/Ti partial replacement affects negatively not only the thermal fluxon motions of correlated two-dimensional pancake vortices but also the ability and strength of vortex lattice period, elasticity, effective and active energy barriers for the flux pinning centers in the Bi-2212 superconducting crystal lattice. In this respect, the Sr/Ti partial substitution mechanism is ploughed to improve the fundamental characteristic features.